ST. LOUIS - Evolution happens. But it can also stop and turn on a dime.

A new study of lizards in the Bahamas shows that the natural selection pressures that drive evolution can flip-flop faster than previously thought - even in months.

"Darwin was right about so many things," said Jonathan Losos, a former Washington University biologist who led the study. "In this case he was wrong. He thought that evolution must occur slowly and gradually."

The lizards and their changing leg lengths are yet another case of evolution occurring in real time. From finches that evolve longer beaks in a few years to bacteria that adapt to strange feeding regimens in days, evolution, as a science, has leapt out of musty museums and into the field.

Scientists say that, from a political perspective, the cases offer a vivid reminder of the continuous process that some people imagine proceeding only in fossilized fits and starts: First monkey, then man.

But for the scientists themselves, the cases show that evolutionary biology has, well, evolved into a predictive, experimental science like any other.

Losos had the perfect Petri dishes: 12 tiny islands in the Bahamas with small populations of insect-eating Anolis sagrei, six-inch long lizards that normally live on the ground but can adapt to life in trees.

On six of the islands, Losos introduced a predator, a large curly-tailed lizard that can gobble up the lizards. He theorized that at first, the fastest prey would survive as they ran for the trees. Natural selection would reward long legs. Then, as the little lizards adapted to life in trees, nimble twig maneuvers and shorter legs would be rewarded.

At the start of the experiment, the scientists, using dental floss nooses on the ends of 10-foot poles, caught all lizards and carefully measured their hind-limbs. After the first six months, their predictions held up. The average leg length of survivors was 2 percent longer than those that were killed. After a year, leg length was 3 percent shorter. The changes were small in absolute terms but statistically very large, said R. Brian Langerhans, a graduate student with Losos.

The study appeared Friday in the journal Science. Losos did the research while at Washington University, but left for Harvard University in June.

The lizard study echoes one of the classic cases of evolution-in-action: Darwin's finches on the Galapagos Islands. For more than 30 years, Princeton University biologists Peter and Rosemary Grant have measured changes in the finches' beaks. After extended droughts, small seeds became more scarce. In a few years, the finches evolved longer beaks to crack the larger, tough seeds that remained. Then as more plentiful times returned, the bird beaks got smaller again.

At Michigan State University, Richard Lenski is studying evolution in test tubes. For almost 20 years, he has reared 12 colonies of E. coli. They have divided more than 30,000 times - which, in terms of human generations, is longer than Homo sapiens has been around. Lenski has challenged the bacteria with strange feeding patterns - feeding them sugars, then starving them.

The colonies all adapted, quickly. But they used different genetic tricks to get there. Their DNA is now remarkably different: an example of parallel evolution.

It's difficult to know how an organism will adapt, and also how subtle environmental changes will kick evolution off in a striking new direction, said Ken Petron, a University of Cincinnati ecologist who worked with the Grants on their finches.

For example, on one trip to the Galapagos during a time of seed scarcity, the Grants expected to find the trend toward larger beaks. But a new, larger finch had colonized the island and was eating the larger seeds, Petron said. It was no longer an advantage for the smaller finches to grow larger beaks.

"It's very difficult to predict the outcome of evolution before it happens," he said.

But if biologists can get better at predicting evolution, it could have applications for areas in which humans are altering the environment and causing evolutionary pressures themselves, Langerhans said. Stanford University ecologist Stephen Palumbi has estimated a $50 billion "evolution bill" associated with the antibiotic and pesticide resistance that bacteria, weeds and insects have evolved in medicine and agriculture.

Had the experiment continued, Losos expected the lizard legs to get even shorter with successive generations. But two hurricanes in quick succession submerged the little islands. "All the living lizards were washed away. Bummer," Losos said.

Some eggs survived, however, and hatchling populations are growing. Losos plans to start the experiment over.

So, we're being told that a previously non-existent gene, the one that causes the generation of longer legs, has appeared recently in the gene pool of this lizard species. Moreover, it seems to have appeared in several separate reproducing individuals among this species more or less simultaneously. Or did I miss something? Who said we no longer live in the Age of Miracles??!!

The more I think about it, the more I believe and know that the Bible is infallible. That being said, I watched a special that aired on the BBC a few weeks back on the birth of the universe. The scientists described, even using some of the same wording found in several translations of the Bible, the birth of the universe. Yes, I think the Bible tells us how the Earth, humans, plants, etc. got here. In a terminology that was understood by the people of the day.

Now what does this make me? Don't ask me. I believe in God Almighty. I believe that evolution happened in some form. I believe He caused it to happen. I also know I don't understand it. I don't like Intelligent Design per se and I don't think this describes my belief on the issue either. But I think about what would be more fantastic, show more care, and frankly give more glory to God. A flip of the fingers six days, and the earth is six thousand years old? Or an evolving over hundreds of millions of years that man finally comes to the point to begin to understand all of creation and even their scientists use the terms found in the Bible from thousands of years ago to describe the beginning of the universe?

RA, I ping you because I'm still torn on the man thing but for me I am beginning to see God's glory in the process of evolution itself. But I can buy your view more. So thank you to you and David Lack.

48
posted on 11/19/2006 2:24:02 PM PST
by billbears
(Those who do not remember the past are condemned to repeat it. --Santayana)

It all hinges on your definition. The authors bill this as "evolution" so it will phase some Darwinists to realize this kind of "evolution" is true. But in the grand scheme, small anatomical variations in species isn't evolution at all.

First, we don't even know if these animals DNA has mechanisms to adapt built in. Legs and beaks (and who knows what else) making small adjustments could actually be a DNA programmed response to the environment the animal finds itself in.

What is even more interesting is the animal tends to return to its previous state when the environmental conditions return to their previous state.

That would seem to be a different mechanism than just "natural selection" branching off in entirely new directions.

No creationist has ever argued against mirco-evolution, which is the change/adaption within a species. It's the straw man in the argument of the evolution from one type of animal become another type of animal, fish to lizard, even cat to dog, or whatever.

Promising mind-numbed newbies are hired to replace the old, worn out hacks when they either 1) move up to a better position somewhere else, 2) "go native" and lose their group-think propaganda mentality.

58
posted on 11/19/2006 2:36:13 PM PST
by x_plus_one
(Franklin Graham: "Allah is not the God of Moses. Allah had no son")

So let me get this straight. You're lecturing Darwinists on what Darwinists believe about evolution? Can you do that with a straight face? Evolution simply refers to a change in allele frequencies over time. Nothing in Darwinian evolution posits any sort of direction to evolution. That's a creationist canard of zero validity. Before you reject science, it might be helpful to have even a passing familiarity with what it is you're rejecting. Otherwise you come off as shallow and ill informed.

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